I was able to gain around 5 HP and 5 TQ on a stock 350z with the little i did. I believe the biggest factor to the gain is the front two runners. But making them all equal length should help aswell.

Keep us informed with your results. If you can do a before and after dyno, since you have two plenums.

Later
Todd

 

I'll go for it...I was also thinking it will help to increase plenum size as well, maybe not by much but it could be a good improvement even if it only shows 1HP - it would be an almost free mod. I'll post results in a few days

 

*be carefull of where you're removing material...some areas don't have that much thickness from the interior to exterior.

can't wait for your results - try to get some good photos of the process.

 

Back in the day, we used to heat-up small block chevy heads in a furnace and then braze the backside of the intake walls so that we could widen them without breaking through.

You could do something similar.

You could heli-arc the backside of the area you want to grind on. Then, when you open up that area, you'd grind through into the weld, not open air. Much easier to do the welding first. Very hard to weld up a hole on thin metal.

 

thought I'd share my progress on my modified upper plenum...haven't had enough time as I'd like, but am almost done; just a few more spots to smooth out and a few more coats of paint:


filling in the 6 bolt holes W/ JB weld - I roughed/drilled the area so it's a very strong interface


filling in other areas so that it's level


paint process


latest pic - after lots of sand paper an coats of paint


the internal side of the plenum has the bolts hole areas entruding about 1/2"...I didn't want to make it 100% flush b/c it'd probably be too week.


Once I finish everything, I'll make another post w/ a complete write-up and photos.

-Peter

 

Wow I thought alot about that despite what has been said about it, but I can't help but think that since this work is being done, to do the same while you're under there. This will not doubt improve the plenum size along with all the other grinding going on there...good job

 

just installed it - work perfectly, no sealing problems.

**after driving more than an hour, i can pop the hood, and place my hand on the plenum - before, the plenum would be too hot to leave my hand there! Cooler plenum, cooler air,...maybe I got 1/5 HP gain from it!

here's the pic of it installed...I wasn't able to make it look perfect b/c of time issues (first AutoX is this Satruday!)

 

Great job on the custom work!

OTOH One significant thing I noticed in the pics. ...Your intake is sitting naked in the engine compartment.

Get that intake shrouded! It will make a real and tangible difference. 120-160 'F Vs 80'F (depending on weather)

40+'F will make a significant difference on ecu's timing curve/power results.

 

I've been tinkering around with ideas of how to do this...I've thought of FG'ing a box, or modifying the OE box, or getting some thin sheet-metal...I like how the ARC box looks, but am planning to DIY. Any other ideas?

thanks,
Peter

 

you could just get the JWT popcharger, or at least use that design if your going to make one

 

yeah...but I'm looking for one more like this:


I'm fairly set on the idea that I'll be making it myself, just haven't figured out how I'll be doing it.

-Peter

 

Other than stock, Stillen has the best heat shroud by far.

Could you fit it over your current filter?

 

I'm thinking more and more of building a shroud out of thin gauge metal - that way I can use ut as an excuse to buy a MIG welder! I doubt the Stillen shroud would fit the AAM intake - either way, I'll have to custom fab it.

-peter

 

Zquicksilver used a tupperware container to take advantage of plastics natural heat resistance...Looked pretty funny but also functional:


Thread:
https://my350z.com/forum/showthread....ght=tupperware

 

wow that ***** halarious...

 

wow - looks like the kinda of stuff I had done to my old '90 Geo...I'm hoping to make something that would resemble a higher quality peice - either way, it'll be a fun process. (I've been reading up on welding units...looks like a decent MIG welder costs near $800)

-Peter

 

NO WAY...my first welder costs $279 and is 110V (yes from your house socket) or to Gas. I own it and one other. For my talon I made 2 custom motor mounts, a complete oil pan. I assembled it's entire exhaust from the downpipe to the magnaflow tip. My prelude has my very own header through the flowmater tip. I did about 90% of that work with my craftsman wirefeed mig. All the exhaust componenets were assembled using a 110V house line and the rest was with shielding gas. Now days you can set yourself up with a wirefeed MIG welder, gloves and helmet for $300 and be up and running 15minutes after opening the box. I don't want to further hijack the thread so just PM if you have any q's

 

Okay I know for sure that I will be milling down the front two runners of my lower plenum. How much should I mill them down? I do have a manual Bridgeport and a CNC Mitsui Seki so I can be accurate within the ten thousandth if need be.

Also, would you guys reccommend an aftermarket plenum (Crawford, Kinetix SSV, or APS) or a plenum spacer (Motordyne or AAM), I will be running FI.

In addition I read this entire thread and Im so glad some people have finally took a step in the right direction and started doing things themselves. Thanks you fellas for being pioneers so the rest of us have something a lil more tried and true when we begin.

 

That looks great!!

I am havings some chunks of metal welded into the holes so that I can completely grind them smooth inside and then if there is visible lines of the welded in material I will weld it from the inside and grind smooth.

I am also going to be milling the front to runners slighly shorter soon and smoothing out some of the lines.

 

I didn't do a before/after measurement of the how much material I took off...I just made sure it was equal amounts for the passenger/driver side. There's a good amount that you can take off, just watch out in some areas b/c the lower plenum isn't too thick on some spots.

great to see some guys with w/ good tools getting into this - keep us posted!

(I just bought a simple welding unit...doubt I'll get a chance to redo the plenum for awhile, but it's on my list!)


-Peter